The invention relates to a digital colour television signal processing circuit comprising an analogue-to-digital converter which is controlled by a pulse generator producing a pulse signal of four times the chrominance subcarrier frequency, a comparison circuit being coupled to the output of the analogue-to-digital converter for comparing different digital burst samples and for obtaining therefrom a control signal for a phase control loop of the pulse generator.
Electronics, Aug. 11, 1981, pages 97-103 describes a colour television signal processing circuit of the above-mentioned type in which samples of the two quadrature components of the burst are compared in order to obtain a control signal which is a measure of the phase difference between the burst and the pulse signal controlling the analogue-to-digital converter. To obtain such a control signal, a function generator (ROM) and an accurate amplitude control are required in order to have the input signal of the function generator maintain the correct amplitude.